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CN1944235B - Electromagnetic-magnetoelectric type micro mechanical resonant beam structure - Google Patents

Electromagnetic-magnetoelectric type micro mechanical resonant beam structure Download PDF

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CN1944235B
CN1944235B CN2006101142749A CN200610114274A CN1944235B CN 1944235 B CN1944235 B CN 1944235B CN 2006101142749 A CN2006101142749 A CN 2006101142749A CN 200610114274 A CN200610114274 A CN 200610114274A CN 1944235 B CN1944235 B CN 1944235B
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resonant beam
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樊尚春
邢维巍
蔡晨光
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Beihang University
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Abstract

电磁-磁电式微机械谐振梁结构,由基体和磁场中的谐振梁构成,以基体弹性膜片和双端固支简单谐振梁构成复合敏感结构,实现输入物理量的谐振式测量。基体和谐振梁采用SOI晶圆,以外延和刻蚀工艺加工而成,基体为低掺杂,谐振梁为N型1×1019cm-3掺杂,二者形成单晶硅整体结构;谐振梁两端具有电极,并与磁场方向正交,通过电流时产生厚度方向的安培力,振动时在两端产生感应电压;采用间歇式原理构成闭环系统,彻底解决了耦合干扰问题。本发明可简化结构和工艺,并有利于改善敏感结构的机械性能和稳定性。

Figure 200610114274

The electromagnetic-magnetoelectric micromechanical resonant beam structure is composed of a matrix and a resonant beam in a magnetic field. The composite sensitive structure is composed of a matrix elastic diaphragm and a simple resonant beam fixed at both ends to realize the resonant measurement of the input physical quantity. The substrate and resonant beams are made of SOI wafers, which are processed by epitaxy and etching processes. The substrate is low-doped, and the resonant beams are N-type 1×10 19 cm -3 doped. The two form an overall structure of single crystal silicon; There are electrodes at both ends of the beam, which are orthogonal to the direction of the magnetic field. When the current passes through it, an Ampere force in the thickness direction is generated, and when it vibrates, an induced voltage is generated at both ends. The intermittent principle is used to form a closed-loop system, which completely solves the problem of coupling interference. The invention can simplify the structure and process, and is beneficial to improve the mechanical performance and stability of the sensitive structure.

Figure 200610114274

Description

Electromagnetic-magnetoelectric type micro mechanical resonant beam structure
Technical field
The present invention relates to a kind of micro mechanical resonant beam structure, mainly as the resonant mode sensing unit in micro mechanical sensor or the inertia device.
Background technology
Resonance beam is the basic functional units in the MEMS device, generally constitutes the composite sensing structure together as final sensing unit and a sensing element.A sensing element, as flexible sheet, issuing looks in measurand q effect should be out of shape; Resonance beam is subjected to corresponding axial tensile force, its resonant frequency f with a sensing element distortion nChange thereupon, thereby at f nAnd set up corresponding relation between the measured q; Obtain f nCan obtain q, Here it is resonant mode sensitive mechanism.
In order to obtain f n, need manage to allow resonance beam be in resonant condition, and detect its resonant frequency f r, therefore need transducer, i.e. vibrator and vibration pickup.Vibrator is a mechanical energy with transformation of electrical energy, makes the resonance beam vibration, and vibration pickup is transformed to electric energy with mechanical energy, obtains the vibration signal of resonance beam.Most transducers all need add other material on resonance beam structure wherein also comprises silica or silicon nitride dielectric layer between transducer and the beam main body, and these materials have constituted additional structure, and have constituted the multilayer materials structure with the resonance beam main body.These technologies are very important to the influence of beam mechanical performance.One solves thinking is exactly to constitute resonance beam with simple conductive material, and is placed in the magnetic field, utilizes electromagnetic force to realize exciting, utilizes electromagnetic induction to realize pick-up, promptly with beam from as electromagnetic actuator and magneto-electric vibration pickup.
Have the prior art based on the micromechanical resonance beam sensor of electromagnetism-magnetoelectricity principle, its adopts binary resonance beam, and two parallel simple harmonic beams are connected as one the H type that forms in midpoint, and a beam is as exciting, and another beam is as pick-up.This technology is the main each several part structure made from the epitaxy technique, the unstability of having avoided a plurality of parts combinations or bonding to introduce.For processing the hanging structure of resonance beam, grown on the backing material epitaxial loayer of a plurality of different levels of doping or polarity of this prior art is a sacrifice layer with some epitaxial loayer wherein, utilizes electrochemical corrosion and heavy doping to stop the erosion technology and removes sacrifice layer, keep required part, and the control structure size.Whole manufacturing process needs at least through 4 extensions and multiple etching, and the manufacturing of its central sill promptly needs the doped epitaxial of 2 variable concentrations, the technology slightly complicated.In addition, because excessive diffusion (out-diffusion) phenomenon of epitaxy technique, the interface between the epitaxial loayer can be tending towards " bluring ", and some occasion heavy doping meeting produces undesirable influence to structural-mechanical property.
Because two simple harmonic beams also are communicated with on electric, have the common mode coupled interference, exciting and pick-up need be coupled through differential transformer.The prior art that the simple harmonic beam that adopts similar technology is also arranged in addition, this technology utilize the impedance operator of resonance beam to realize exciting and pick-up, and the coupled interference problem more is difficult to solve.
Summary of the invention
The technical problem to be solved in the present invention: overcome the deficiencies in the prior art, provide a kind of and can solve the coupled interference problem well, and simple in structure, practical electromagnetic-magnetoelectric type micro mechanical resonant beam structure.
Technical solution of the present invention: electromagnetic-magnetoelectric type micro mechanical resonant beam structure, constitute by the resonance beam in matrix and the magnetic field, matrix comprises a flexible sheet that is out of shape with measurand, the resonance beam two fixed ends is in the flexible sheet surface, its intrinsic frequency changes with flexible sheet, realizes that the resonant mode of input physical quantity is measured; Matrix and resonance beam adopt the SOI wafer, process with extension and etching technics; The resonance beam two ends have electrode, and with the magnetic direction quadrature, produce the Ampere force of thickness direction during by electric current, produce induced voltage at two ends during vibration, adopt the work of batch (-type) mode to constitute closed-loop system, with thorough solution coupled interference problem.
Described magnetic field adopts permanent magnet or solenoid to produce, and the phase different pole is positioned at the resonance beam both sides, thus magnetic field pass resonance beam and with its length direction and thickness direction quadrature.
The SOI wafer that described matrix and resonance beam adopt is by SiO 2Buried layer (BOX), monocrystalline silicon layer (SCS) and substrate are formed, BOX bed thickness 1~2 μ m; The SCS layer is N type (mixing phosphorus), doping content about 1 * 10 19~2 * 10 19Cm -3, thick about 4~10 μ m, substrate is low-doped N type.
Described matrix and resonance beam adopt the SOI wafer, and be as follows with extension and etching technics processing method:
(1) utilize etching technics that the SCS layer and the BOX layer of described SOI wafer are carried out selective removal, with the reserve part of BOX layer as sacrifice layer;
(2) in body structure surface growth N type 1 * 10 19Cm -3First epitaxial loayer that mixes, the reserve part and the substrate of connection SCS layer constitute the monocrystalline silicon overall structure;
(3) deposit TEOS utilizes the chemically mechanical polishing complanation, regrows second epitaxial loayer of same doping, constitutes new monocrystalline silicon overall structure;
(4) utilize selective etch to remove remaining SiO 2, discharge the resonance beam that both-end props up admittedly; Epi-layer surface outside the resonance beam two ends is made electrode, with connecting circuit.
Described employing service intermittent mode constitutes closed-loop system and comprises exciting circuit, resonance beam, testing circuit and control circuit, and in foment, control circuit control exciting circuit output accumulation signal makes the resonance beam starting of oscillation; At detected state, control circuit control exciting circuit cuts out accumulation signal, resonance beam freedom of entry vibrational state, amplitude is decayed gradually but still can be kept a period of time, the detection and the amplification of pick-up signal are carried out in the utilization of control circuit control testing circuit during this period of time, treat resonance beam near the failure of oscillation state, and exciting circuit is exported accumulation signal once more, make resonance beam starting of oscillation once more, so repeat.
Principle of the present invention: exciting of the present invention and pick-up principle are as shown in Figure 2.Two resonance beam 2 are same beam among the figure, the situation of 2 exciting functions of last figure expression resonance beam, and figure below is represented the situation of 2 pick-up functions of resonance beam.Two end faces at resonance beam 2 two ends promptly adopt both-end to prop up mode admittedly for propping up face 41 admittedly.Among the figure, the x axle is the length direction of resonance beam 2, also is sense of current, and the z axle is the thickness direction of beam, also is direction of vibration, and the y axle is the width of resonance beam 2, also is the roughly direction in magnetic field.If pass y axle component being distributed as of the magnetic induction intensity of resonance beam 2 along the x axle
Figure GSB00000328561300031
Flow through alternating current i (t) in the resonance beam 2, then the suffered z of infinitesimal dx to Ampere force is
Figure GSB00000328561300032
According to right-hand screw rule, Direction is z axle (thickness) direction, so resonance beam 2 is subjected to the alternation active force of thickness direction and starting of oscillation.
Principle of the present invention: exciting of the present invention and pick-up principle are as shown in Figure 2.Among the figure, the x axle is the length direction of resonance beam 2, also is sense of current, and the z axle is the thickness direction of beam, also is direction of vibration, and the y axle is the width of resonance beam 2, also is the roughly direction in magnetic field.If pass y axle component being distributed as of the magnetic induction intensity of resonance beam 2 along the x axle Flow through alternating current i (t) in the resonance beam 2, then the suffered z of infinitesimal dx to Ampere force is According to right-hand screw rule,
Figure GSB00000328561300041
Direction is z axle (thickness) direction, so resonance beam 2 is subjected to the alternation active force of thickness direction and starting of oscillation.
When resonance beam 2 vibrations, resonance beam 2 two ends produce the alternating current impression electromotive force.If the z of beam to instantaneous velocity is
Figure GSB00000328561300042
Then induced electromotive force is
Figure GSB00000328561300043
Wherein L is resonance beam 2 effective lengths.Only consider single order mode, then each point Homophase, and the hypothesis load resistance is enough big, then can obtain the interchange pick-up voltage v of reflection resonance beam transient vibration state at resonance beam 2 two ends i(t)=E (t).
Obtain v i(t) just solved the pick-up problem, but the detection of pick-up signal remains a difficult problem.Resonance beam 2 of the present invention is the simple harmonic beam, frame for movement and electrical structure overlap fully, so exciting and pick-up can only shared conductors (resonance beam), faint pick-up signal is flooded by accumulation signal fully, adopts conventional method to be difficult to really realize both decoupling zeros.Can use for reference batch (-type) (Burst) principle that people such as Thierry Corman, Kjell Nor é n propose in paper " " Burst " Technology with Feedback-Loop Control for Capacitive Detection and Electrostatic Excitation of Resonant Silicon Sensors " for this reason.But concrete principle of the present invention is different with it.Though this paper has adopted the intermittent drive mode, but still attempt to make working sensor in the continuous shaking state, because sensor output signal is very faint, and phase place is very sensitive to noise, actual difficult reliable realization of continuous shaking, and related circuit is also complicated.Therefore the present invention adopts " intermittent control shaking " but not " intermittent drive " principle that this paper proposes makes resonance beam really work in the batch (-type) vibrational state, and its basic sequential as shown in Figure 3.In foment, circuit output accumulation signal makes the resonance beam starting of oscillation; At detected state, close accumulation signal, resonance beam 2 freedom of entry vibrational states, amplitude is decayed gradually but still can be kept a period of time, and the detection and the amplification of pick-up signal carried out in the testing circuit utilization during this period of time; Treat resonance beam 2 near the failure of oscillation state, circuit is exported accumulation signal once more, makes resonance beam starting of oscillation once more, so repeats.Compare with the detection method based on differential transformer coupling or impedance operator in the prior art, this method has thoroughly solved the coupled interference problem, and does not need the interference isolating device of transformer and so on.
SOI (monocrystalline silicon on the insulator) is the wafer material of " SCS-BOX-substrate " three-decker.In MEMS processing, an important use of BOX layer is exactly " prefabricated " sacrifice layer.SiO 2Good with Si corrosion selectivity, and coefficient of thermal expansion is approaching, thereby SiO 2It is desirable sacrificial layer material.SCS-BOX interface quality height in the SOI wafer utilizes the BOX sacrifice layer can obtain good thickness and precision and surface quality, so the present invention adopts the SOI wafer, and is the space of sacrifice layer processing resonance beam bottom with its BOX.
The present invention's advantage compared with prior art: adopt SOI wafer and wet etching technique, technology is simple; BOX layer with the SOI wafer is the space of sacrifice layer processing resonance beam bottom, and structure precision and surface quality are good; Resonance beam mainly is made of epitaxial loayer, and need not heavy doping, is convenient to control structure stress, is convenient to obtain comparatively ideal epitaxial loayer; Epitaxial loayer is highly doped, and substrate is low-doped, helps eliminating autodoping effect, good manufacturability; Employing batch (-type) principle has realized the decoupling zero between accumulation signal and pick-up signal, and the simple harmonic girder construction that frame for movement and electrical structure are overlapped really obtains practicality.
Description of drawings
Fig. 1 is a structural representation of the present invention;
Fig. 2 is exciting of the present invention and pick-up principle schematic;
Fig. 3 is the sequential schematic diagram of batch (-type) principle of the present invention;
Fig. 4 is a basic process steps of the present invention;
Fig. 5 realizes the principle schematic of closed-loop system for the batch (-type) principle;
Fig. 6 is the cross sectional representation of first kind of space arrangement of field generator for magnetic;
Fig. 7 is the cross sectional representation of second kind of space arrangement of field generator for magnetic;
Fig. 8 is the sensitive structure schematic diagram of the resonance type pressure sensor of employing the present invention formation;
Fig. 9 is the sensitive structure schematic diagram of the resonance type accelerometer of employing the present invention formation.
The specific embodiment
As shown in Figure 1, the present invention is by matrix 1 and place the resonance beam 2 of magnetic field B (x) to constitute, matrix 1 is for changing the flexible sheet that strain takes place with measurand, resonance beam 2 two fixed ends are in matrix 1 surface, its intrinsic frequency changes with matrix 1, realizes that the resonant mode of input physical quantity is measured; Matrix 1 and resonance beam 2 adopt the SOI wafer, process with extension and etching technics; Resonance beam 2 two ends have electrode, and and magnetic field
Figure GSB00000328561300061
The direction quadrature, produce the Ampere force of thickness direction during by electric current, produce induced voltage at two ends during vibration, adopt the batch (-type) principle to constitute closed-loop system, with thorough solution coupled interference problem.
As shown in Figure 4, the SOI wafer of matrix 1 and resonance beam 2 employings is by monocrystalline silicon layer 13, SiO 2Buried layer 12 and substrate 11 are formed.Shown in Fig. 4 a, SiO 2Buried layer 12 thick 1~2 μ m; Monocrystalline silicon layer 13 is N type (mixing phosphorus), doping content 1 * 10 19~2 * 10 19Cm -3, thick 4~10 μ m; Substrate 11 is low-doped N type.
Structure of the present invention mainly relies on technologies such as above-mentioned SOI wafer being adopted extension and wet etching and obtains concrete steps following (wherein having omitted general mask graph photo-mask process):
(1) shown in Fig. 4 b, with SiO 2Buried layer 12 for stop the layer monocrystalline silicon layer 13 is carried out etching, obtain second monocrystalline silicon layer 15, be mask with second monocrystalline silicon layer 15, with substrate 11 for stopping layer, to SiO 2Buried layer 12 carries out etching, obtains the 2nd SiO 2Buried layer 14.The 2nd SiO 2Buried layer 14 will be as the sacrifice layer of subsequent technique.
(2) shown in Fig. 4 c, with the 2nd SiO 2Buried layer 14 carries out etching for stopping layer to second monocrystalline silicon layer 15, obtains and following the 3rd corresponding monocrystalline silicon layer 16 of resonance beam.Because Fig. 4 (b) body structure surface exists by the 2nd SiO 2High " I-shaped " boss of 5~12 μ m that the buried layer 14 and second monocrystalline silicon layer 15 constitute has not been complete plane, and for guaranteeing photoetching quality, the deposit polyimides carry out surfacingization, at polyimide surface deposit TEOS, applies photoresist at last afterwards.During etching, according to photoresist → SiO 2The order transition diagram of → polyimides → SCS is removed mask material at last.Answer the error of compensation figure transfer process during layout design, and for avoiding the marginal portion of boss, the 3rd monocrystalline silicon layer 16 of rectangle is than the 2nd SiO of its below 2The counterpart of buried layer 14 slightly shortens.
(3) as Fig. 4 d: at Fig. 4 c body structure surface growth 6~12 μ m doping contents and the first approaching epitaxial loayer 17 of the 3rd monocrystalline silicon layer 16.Because the intrinsic selectivity of epitaxy technique, epitaxial loayer only can be grown in the surface of the 3rd monocrystalline silicon layer 16 and substrate 11 expose portions, so first epitaxial loayer 17 has the H type structure among the figure.Because the intrinsic local effect of epitaxy technique, the thickness of substrate surface epitaxial loayer is greater than the thickness of the 3rd monocrystalline silicon layer 16 surperficial epitaxial loayers, so epitaxy layer thickness should be as the criterion with the former.
(4) shown in Fig. 4 e, at the TEOS of the about 15 μ m of Fig. 4 d body structure surface deposit, fill low recess, carry out chemically mechanical polishing (CMP) then, obtain complete planar surface; Carry out a chemical polishing afterwards again, with further elimination skin stress.The removal amount of chemical polishing should approach (0.5 μ m is following) as far as possible, avoids reducing surface flatness.At this moment, to answer attenuate be that the 4th monocrystalline silicon layer 18, the first epitaxial loayers 17 corresponding attenuates of 1~2 μ m are second epitaxial loayer 19 of 2~4 μ m to the 3rd monocrystalline silicon layer 16.
(5) shown in Fig. 4 f, with the doping content of step (3) at the 4th monocrystalline silicon layer 18 and second epitaxial loayer, 19 surface selectivity growth regulations, three epitaxial loayers 20.The thickness of the thickness decision resonance beam of the 3rd epitaxial loayer 20, for example the 3rd epitaxial loayer that 4 μ m are thick will obtain the thick resonance beam of 6~8 μ m.
(6) shown in Fig. 4 g, the 4th monocrystalline silicon layer 18, second epitaxial loayer 19 and the 3rd epitaxial loayer 20 constitute 1 * 10 at this moment 19~2 * 10 19Cm -3The monocrystalline silicon overall structure of mixing is referred to as superstructure 21; 21 solid districts of widening by both sides 22 of superstructure form the monocrystalline silicon overall structure with substrate 11.Adopt the HF wet etching to remove all remaining SiO 2, discharging resonance beam 2, resonance beam 2 is made up of the 3rd epitaxial loayer 20 interludes and the 4th monocrystalline silicon layer 18, has 1~2 μ m safe distance, i.e. SiO with the substrate 11 of below 2The thickness of buried layer.
(7) make electrode on 22 surfaces, solid district, finally obtain structure shown in Figure 1.
(8) substrate 11 is processed, made its function, specifically see below the discussion of matrix 1 embodiment with responsive specific physical quantity.
Above-mentioned technology only needs 1~2 extension, and the process conditions of 2 extensions are identical, and adopt wet etching fully, do not need dry etching and electrochemical corrosion, thereby technology are simple, and cost is lower.Utilize the monocrystalline silicon layer and the epitaxial loayer of SOI wafer to constitute resonance beam, doping content is moderate, and does not have foreign material on the monocrystalline silicon overall structure except that electrode, and heat endurance is guaranteed.Because substrate doping is very low, and outer layer doping concentration is higher, helps avoid autodoping effect, good manufacturability.
Choosing of each several part doping content, mainly consider process conditions, insulation/electric conductivity and mechanical performance.Consider that from insulating properties substrate is an optimum with intrinsic monocrystalline silicon, but actual being difficult to accomplishes that be as the criterion so be not less than 50 Ω cm with body resistivity, this moment, the doping content upper limit about 10 14Cm -3Consider that from electric conductivity the doping content of superstructure should be high as far as possible, but, adopt 1~2 * 10 for the epitaxial layer quality of avoiding lattice mismatch to cause descends and serious internal stress 19Cm -3Doping content.This moment, lattice mismatch was very little, and body resistivity about 5 * 10 -3Ω cm, length * wide * thick=800 * 80 * 8 μ m 3About 63 Ω of resistance of resonance beam, enough little from the circuit design angle.
Resonance beam 2 bottoms 2 μ m are from monocrystalline silicon layer 13, if its doping content is lower than second epitaxial loayer 20) doping content, the internal stress that produces will make resonance beam that recessed trend is arranged, and reduce the safe distance of 11 of resonance beam 2 and substrates, can make the two contact when serious and cause structural failure.From this angle, the doping content of monocrystalline silicon layer should be a little more than epitaxial loayer, and for example 2.5 * 10 19Cm -3But such SOI wafer can't directly obtain sometimes, and can increase monocrystalline silicon layer 13 and expand the phosphorus operation this moment.
Adopt the service intermittent mode to constitute closed-loop system as Fig. 3, Fig. 5 and comprise exciting circuit, resonance beam, testing circuit and control circuit, in foment, control circuit control exciting circuit output accumulation signal makes the resonance beam starting of oscillation; At detected state, control circuit control exciting circuit cuts out accumulation signal, resonance beam 2 freedom of entry vibrational states, amplitude is decayed gradually but still can be kept a period of time, the detection and the amplification of pick-up signal are carried out in the utilization of control circuit control testing circuit during this period of time, treat resonance beam 2 near the failure of oscillation state, and exciting circuit is exported accumulation signal once more, make resonance beam starting of oscillation once more, so repeat.
Exciting circuit adopts the signal generating circuit based on Direct Digital synthetic (DDS) or voltage controlled oscillator (VCO), testing circuit comprises links such as low-noise amplifier and noise filter, and control circuit comprises A/D, D/A and microcontroller (MCU) or digital signal processor parts such as (DSP), but the different application occasion may be made very various specific design, those skilled in the art are easy to realize, will not describe in detail here.
For the generating means of the magnetic field B among the present invention (x),, two kinds of typical embodiment are arranged from the angle of space arrangement.But no matter adopt any space arrangement, the magnetic line of force that all requires to pass beam is similar to parallel with the y axle.
(1) two block of small-sized magnet 23 is arranged in the position of very close resonance beam 2 on the micro mechanical device, and heteropole is relative, and opposing magnetic pole connects (not drawing among the figure) with magnetic conductor, as shown in Figure 6.The magnet of this mode and magnetic conductor are all less, help reducing the volume and weight of whole micro mechanical device; The magnetic circuit scope is little, and magnetic strength leaks little; But difficulty is installed in processing.
(2) two blocks of large-scale magnet 24 are arranged in the both sides of whole micro mechanical device, and heteropole is relative, and opposing magnetic pole connects (not drawing among the figure) with magnetic conductor, as shown in Figure 7.The magnet of this mode and the volume and weight of magnetic conductor are all bigger; The magnetic circuit scope is big, and magnetic strength leaks also bigger; Other parts of sensor also may be in the magnetic field, if these parts then may have a negative impact to magnetic-field-sensitive; But the processing of this structure is installed easily, as long as take suitable magnetic screen measure, still is worth attempting in a lot of concrete occasions.
Structure of the present invention can be used for measuring multiple physical quantity.By matrix 1 structure is designed, make it to specific physical quantity sensitivity, produce corresponding deformation with this physical quantity, and produce corresponding tension force at resonance beam 2 two ends, just can constitute the sensor (sensitive structure) that detects this physical quantity.Below be two kinds of exemplary embodiment.
Make matrix 1 responsive distribution pressure, can constitute the presser sensor structure, as shown in Figure 8.Adopt anisotropic etching at substrate 11 back sides processing deep trouth, the thick portion around the deep trouth becomes isolated area, and the deep trouth bottom thin film becomes flexible sheet 4; Isolated area 33 and the airtight bonding in glass base 34 4 limits; Vacuum orifice 31 by level Hermetic Package 32 is extracted inner air out, seals vacuum orifice 31 afterwards, can realize vacuum in inside, effectively improves the quality factor of resonance beam 2; Deflection takes place in flexible sheet 4 under well-distributed pressure 36 effects, make two solid ends of beam that relative displacement take place, the resonant frequency (displacement → axial tensile force → axial stress → rigidity → resonant frequency) of control beam, thus set up corresponding relation in resonant frequency and between by measuring pressure.One group of canonical parameter is: range 0~350kPa, elastic membrane length of a film * wide * thick=2 * 2 * 0.2mm 3, resonance beam length * wide * thick=800 * 80 * 8 μ m 3
Matrix 1 to above-mentioned pressure sensor is made an amendment slightly, the back side utilizes bonding technology quality of connection piece 37, is m together with flexible sheet 4 equivalent mass own, makes flexible sheet 4 experience the concentrated force F=ma that acceleration a produces, can constitute the acceleration sensitive structure, as Fig. 9.This moment do not have airtight problem, so diaphragm only combine with base on the both sides on the beam length direction, with the raising sensitivity.

Claims (5)

1.电磁-磁电式微机械谐振梁结构,由基体(1)和磁场 
Figure RE-F200610114274901C00011
中的谐振梁(2)构成,基体(1)包括一个随被测物理量变化而变形的弹性膜片,谐振梁(2)两端固支于弹性膜片表面,其固有频率随弹性膜片变形而变化,实现输入物理量的谐振式测量;基体(1)和谐振梁(2)采用同一块SOI晶圆,以外延和刻蚀工艺加工而成;谐振梁(2)两端具有电极,并与磁场 方向正交,通过电流时产生厚度方向的安培力,振动时在两端产生感应电压,采用间歇式工作方式构成闭环系统。
1. The electromagnetic-magnetoelectric micromechanical resonant beam structure consists of a substrate (1) and a magnetic field
Figure RE-F200610114274901C00011
The resonant beam (2) is composed of the resonant beam (2), the matrix (1) includes an elastic diaphragm that deforms with the change of the measured physical quantity, the two ends of the resonant beam (2) are fixed on the surface of the elastic diaphragm, and its natural frequency changes with the deformation of the elastic diaphragm change, to realize the resonant measurement of the input physical quantity; the substrate (1) and the resonant beam (2) are made of the same SOI wafer, processed by epitaxy and etching; the resonant beam (2) has electrodes at both ends, and is connected with the magnetic field The direction is orthogonal, the ampere force in the thickness direction is generated when the current is passed, and the induced voltage is generated at both ends when the vibration is performed, and the intermittent working mode is adopted to form a closed-loop system.
2.根据权利要求1所述的电磁-磁电式微机械谐振梁结构,其特征在于:所述的磁场 采用永磁体或电磁线圈产生,相异磁极位于谐振梁(2)两侧。2. The electromagnetic-magnetoelectric micromechanical resonant beam structure according to claim 1, characterized in that: the magnetic field It is generated by a permanent magnet or an electromagnetic coil, and the different magnetic poles are located on both sides of the resonant beam (2). 3.根据权利要求1所述的电磁-磁电式微机械谐振梁结构,其特征在于:所述的基体(1)和谐振梁(2)采用的SOI晶圆由衬底(11)、SiO2掩埋层(12)、单晶硅层(13)组成,SiO2掩埋层(12)厚1~2μm;单晶硅层(13)为掺杂N型,掺杂浓度1×1019~2×1019cm-3,厚4~10μm;衬底(11)为低掺杂N型。3. The electromagnetic-magnetoelectric micromechanical resonant beam structure according to claim 1, characterized in that: the SOI wafer used in the base body (1) and resonant beam (2) is made of substrate (11), SiO 2 The buried layer (12) is composed of a single crystal silicon layer (13), the SiO 2 buried layer (12) is 1-2 μm thick; the single crystal silicon layer (13) is doped with N type, and the doping concentration is 1×10 19 to 2× 10 19 cm -3 , 4-10 μm thick; the substrate (11) is low-doped N-type. 4.根据权利要求1所述的电磁-磁电式微机械谐振梁结构,其特征在于:所述的基体(1)和谐振梁(2)采用SOI晶圆,以外延和刻蚀工艺加工,其加工方法如下:4. The electromagnetic-magnetoelectric micromechanical resonant beam structure according to claim 1, characterized in that: the base (1) and the resonant beam (2) adopt SOI wafers, processed by epitaxy and etching processes, and The processing method is as follows: (1)利用刻蚀工艺对所述SOI晶圆的单晶硅层(13)和SiO2掩埋层(12)进行选择性去除,将SiO2掩埋层(12)的保留部分用作牺牲层;(1) using an etching process to selectively remove the monocrystalline silicon layer (13) and the SiO2 buried layer (12) of the SOI wafer, and use the remaining part of the SiO2 buried layer (12) as a sacrificial layer; (2)在结构表面生长N型掺杂浓度与单晶硅层(13)接近的第一外延层(17),连接单晶硅层(13)的保留部分与衬底(11),构成单晶硅整体结构;(2) grow a first epitaxial layer (17) with an N-type doping concentration close to that of the monocrystalline silicon layer (13) on the surface of the structure, and connect the remaining part of the monocrystalline silicon layer (13) with the substrate (11) to form a monocrystalline silicon layer (13) The overall structure of crystalline silicon; (3)淀积TEOS,利用化学机械抛光平面化,再次生长同样掺杂的第 二外延层(20),构成新的单晶硅整体结构; (3) depositing TEOS, utilizing chemical mechanical polishing to planarize, and growing the second epitaxial layer (20) of the same doping again to form a new monocrystalline silicon overall structure; (4)利用选择性刻蚀去除剩余的SiO2,释放出双端固支的谐振梁(2);在谐振梁(2)两端之外的外延层表面制作电极,以连接电路。 (4) Selective etching is used to remove the remaining SiO 2 to release the resonant beam ( 2 ) fixed at both ends; electrodes are made on the surface of the epitaxial layer other than the two ends of the resonant beam ( 2 ) to connect the circuit. 5.根据权利要求1所述的电磁-磁电式微机械谐振梁结构,其特征在于:所述的采用间歇式工作方式构成的闭环系统包括激励电路、谐振梁、检测电路和控制电路,在激励状态,控制电路控制激励电路输出激振信号,使谐振梁起振;在检测状态,控制电路控制激励电路关闭激振信号,谐振梁(2)进入自由振动状态,振幅逐渐衰减但仍能保持一段时间,控制电路控制检测电路利用这段时间进行拾振信号的检测和放大,待谐振梁(2)接近停振状态,激励电路再次输出激振信号,使谐振梁再次起振,如此重复。 5. The electromagnetic-magnetoelectric micromechanical resonant beam structure according to claim 1, characterized in that: the closed-loop system formed by the intermittent working mode includes an excitation circuit, a resonant beam, a detection circuit and a control circuit, and when the excitation state, the control circuit controls the excitation circuit to output an excitation signal to make the resonant beam start to vibrate; in the detection state, the control circuit controls the excitation circuit to turn off the excitation signal, and the resonant beam (2) enters a free vibration state, and the amplitude gradually decays but can still be maintained for a period of time. The control circuit controls the detection circuit to use this period of time to detect and amplify the vibration pickup signal. When the resonant beam (2) is close to the vibration stop state, the excitation circuit outputs the excitation signal again to make the resonant beam start to vibrate again, and so on. the
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